Where did you read she was a lesbian?
Google
Tilda Swinton + lesbian = Planetout.com
Looks like she's had a lot of lesbian roles.
First, the planetout.com link to her said nothing about her being a lesbian. So she's had some lesbian roles? Sure, I'd bet everything I have she's a huge lib, but that doesn't make her a lesbian.
Everything I've found on Tilda Swinton says that she's married to some guy named John Byrne and they have two kids.
Please show me something that explicity states she's a lesbian.
And Roles = life?
Hilary Swank didn't have a sex change just because she played a guy!